Water Footprinting of beef and sheep production

Agricultural production consumes significant amounts of natural resources, including water, along the supply chain. Sustainable management of water in agriculture is critical to maintaining environmental integrity, which is necessary to satisfy a growing global demand for animal sourced food. The main objective of this study was to determine the freshwater consumption, expressed as a water footprint, and the associated impacts for the production of 1 kg of beef and sheep meat. Irish pasture-based farms were used as a case study; however the methods described could be applied to any type of livestock production system.

Water-footprints have become an important sustainability indicator in the context of intensification of agricultural production. A water-footprint is defined as the sum of the volumetric water use along the entire supply chain of a product. The water-footprint approach used in this study quantified the volumetric blue (ground and surface water), and green (soil moisture due to evapotranspiration) water-footprints. One of the biggest hurdles in completing a water-footprint is the lack of available data at farm level to allow accurate calculations. To achieve this level of detail, data were collected directly from 10 beef farms and six lowland sheep farms. To capture the farm-to-farm and temporal variability, data was collected on a monthly basis for two consecutive years.

Freshwater use included water required for the cultivation of crops for concentrate feed, on-farm cultivation of grass or fodder and water required for animal husbandry and farm maintenance. The outputs were expressed per kg of carcass weight. The impact of blue water consumption on global water stress due to the production of beef and sheep meat was also computed in the form of a stress-weighted water-footprint.

The average water-footprint of the beef farms was 8391 litres per kg of carcass weight; 98% of this was classified as green water whereas only 2% was classified as blue water. The average water-footprint of the sheep farms was 7672 litres per kg of carcass weight; 99% of this was classified as green water whereas just 1% was classified as blue water. Green water for grass growth contributed 88% and 87% to the water-footprint of Irish beef and sheep farms, respectively. The stress-weighted water-footprint of beef was 91 litres of water equivalent per kg of carcass weight, implying that each kg of beef produced contributed to freshwater scarcity equivalent to the consumption of 91 litres of freshwater by an average world citizen. The average stress-weighted water-footprint for sheep was 2 litres of water equivalent per kg of carcass weight

Hence, since the majority of water used on the case study farms was green water, this study concluded that converting the water used to grow grass (i.e. green water) into a human food source (i.e. animal source food) with minimal blue water inputs could be considered a sustainable use of water resources.